Hello all,
 
I have sonar X1 LE and I want to upgrade to Sonar professional. I am afraid that after upgrade I will not be able to open my old projects made by Sonar X1 LE. Can anyone give me an advice?

Hi, and welcome to this forum. You should have no problems opening older projects. You might get the "missing plugin" message if you do not have the same plugins you did when creating it, but that should be the only issue.
You could also try the demo, to see for yourself here. https://www.cakewalk.com/Products/SONAR/Try-SONAR#start
All the best.

In my experience Sonar is pretty rock-solid in terms of backwards compatibility, I've never run into a problem. I have heard of issues with old Bundle (.bun) files but I've never used those so I can't comment. Of course, you need to have all the resources the project used - audio files, plugins - but other than that, it should be smooth sailing...

As already stated, try the demo.
 
Also, worst case, you can keep X1 LE installed just in case. (Older versions normally work side by side with new ones).

Should be no issue with opening up files. And through the end of the month you can save $50 off the upgrade price.